Method of utilizing combustion gases



Feb. 27, 1940. c. A. DUNHAM ETAL METHOD OF UTILIZING COMBUSTION GASESFiled DSG. 27, 1937 ylo Patented Feb. 27, 1940 a a `2,191,985 METHOD orUTILIZING cotoeUs'moN GAsss Clayton A. Dunham and. Aubra R. Dunham,Glencoe, Ill., assignors to Experimental Laboratories, Incorporated,Chicago, Ill., a corporation of Illinoisv Application December 27,1937,serial No. 181,905

y Claims.

This invention relates to a method of utilizing combustion gasescontaining sulphur in, for example, heating systems or in power plants;and the primary object of the invention is. to provide a new andimproved method for the utilization ofy such gases which will preventcorrosion of surfaces with which such gases come into contact, such asmetalsurfaces, for instance, by insuring the dilution of sulphuric acidin the condensateto a point at which the acid is substantiallynon-corrosive.`

The invention has for one of its particular objects, the prevention ofcorrosion in a heating systeniof the type in which the heating mediumconsists of a mixture of the products of combustion of fuel gas, oil orcoal, and water vapor; the 'invention being of special value ina systemin which the temperature of the heating medium in itscirculation'through the radiating system is reduced vto give a lowoutlet hue temperature for the purpose of effecting economy ofoperation. In heating systems using combustiongases containing watervapor resulting from combustion, or such Water vaporplus Water vaporadded to the products of comhustion,it has been found necessary tocirculate and exhaust the heating medium at wasteiully high temperaturesin order to prevent condensation and the formation of .strong sulphuricvacid, as the heat in these gases is given up in the system at lcertainintermedi ate temperature ranges, with consequent corrosion ordeterioration of piping and other metal parts. Heating systems employingsuch ymixtures as their heating media have not always l:35; provedreconomical, eilicient,` or entirely praction other materials such ascommon flue mate-l .':0 rials. As the temperaturev of the medium isstill further reduced belowv the strong acid dew` point,

a vtemperature ranger will ultimately be reached vat which water willcondense 'in such excess as to prevent appreciable corrosion. But atplaces 55 in the system'in advance of this, Where medium corrosiveaction, not` only on ironl tains any substantial quantity of sulphur, asis the case with oil, coal and most manufactured fuel gases.

In accordance with the present invention, corrosion is prevented byadding to the combustion gases a relatively large quantity of watervapor so that wherever condensation of acid takes place, the water willbe in such excess over the sulphurcompounds condensing out atthe sametime' that the latter will be diluted to a substantially non-corrosivestate. `ly insuring a mixture of thischaractenit is possible to reduceoutlet ue temperatures lto such a degree as to make this type of heatingprocess very practical and economical. Preferably the system will beoperated under a slight vacuum, say a, fraction of an inch of mercuryfor two purposes: lust, to insure against escape of gases from thesystem into roomsy in case of leakage; and second, because. thecorrosive effect of such acid asthere may be in the condensate isen`lhancedby4 increase of pressure and temperature. The' initialtemperature of the heating medium, las it comes from the generator andenters the heating system, will ordinarily be betWeenlQvO" and 212 F,and theoutlet flue temperature between lll()o F. and 120 The dew pointdepends upon three factors: the amount of sul-` phur, sulphur raisingthe dew pointythe amount of air inthe mixture which tends to lower thedew point, but the presence'of which decreases efficiency; andthearnount of water vapor present, which latter will be the sum of theWater produced by combustion and that added at the generator. "Thewaterr added at the generator is, of course, the dew pointcontrollingfactor, in accordance with the present invention; and in order to insureagainst corrosion it has lbeen found necessary, under ordinary practicalconditions to increase theuwater vapor content of the medium so that thevresulting condensate will notcontain at anytime more than a fraction of1% of sulphuric acid. In order to be as `safe as possible, it isdesirable to have the medium f saturated at approximately atmosphericpressure and at an initial temperature of 190 to 212".F. This, however,is'not ordinarily essential, and initial saturation at about 175 F., oreven somewhat'lower, will be suicient if a fuel gas is usedgcontaninggrains of sulphur per 100. cubic feet, or other fuels with usual Byconstant- ,i

temperatures jprevail, condensation of strong l sulphur contents. `Underordinary conditions the amount of water vapor in the medium at 190 F.should be from 25%, by volume, up to saturation.

The application of the invention to practice is illustrated in the-accompanying drawing which is a diagramv of a heating system suitablefor practicing the process of this invention.

Referring to the drawing, l designates the generator which is shown.diagrammatically but is not claimed herein being claimed in copendingapplication, Serial No. 183,048, iiled January 3, 1938, now Patent No.2,169,683, granted August 15, 1939. The generator is formed with a waterspace Z, and a combustion chamber 3 in which is located a burner il,supplied by gas pipe 5. The

products of combustion pass through ducts 6 and 1, where they are mixedwith water whichy is forced from space 8 through ducts 9 into the re,-ceptacle Hi over the'edge of which the water flows intothe upwardlymoving current of combustion gases. The mixture containing the properquantity of water vapor, in accordance with the princi` ples of theinvention hereinabove set forth, (insured by the use of a generator asdescribed which operates in fact to give substantial saturation at190-212 F.) passes through the supply main H to the radiators lil- 52,the radiators being connected to the supply main by risers l3-l3 and tothe return main M by down pipes !5-I5. A water seal i@ may be interposedbetween the' sup ply main and return main. The return main I4 isconnected with an exhauster il', the eduction pipe I8 of whichconstitutes the vent pipe of the system. Leading from the return main isa con densate return pipe I9 which is connected with the water space ofthe generator at 2B and with a pipe 2i connected with supply main l land having therein an overflow pipe 22 which through water seal 23delivers into drain pipe 243. A pipe 25, having a water seal 26, mayconnect the exhauster with drain pipe Z. Under ordinary con-- ditions ofoperation, the water produced by coinbustion will be sufficient for theneeds of the system with some excess which passes out through pipe 2t.Additional water may be introduced into the system, automatically orotherwise,'froin pipe `2l: or the returned water might be chemicallytreated to reduce acidity.

In the preferred operation of the system as disclosed, the exhauster andgas supply will be automatically controlled by a room thermostat 28,this speciiic control mechanism, however, form-e ing no part of thepresent invention. However, the use of such a thermostatic controlresults in the intermittent use of the generator, that is the combustionprocess isstarted and stopped at rather short intervals. Consequently itis necessary that a generator be used which will start the Vaporizingand saturating process almost immediately after the combustion processhas been restarted so that there` will be no substantial periods of timein which the combustion gases will be insufficiently saturated. Thegenerator herein diagrammatically disclosed, and disclosed more indetail in said copending application, is

v particularly adapted for this purpose.

In carrying out the invention in its preferred form, it is the aim tomaintain relatively low stack temperature, temperatures far below thedew point for the water vapor from the gas, so that the latent heat inthe water vapor is utilized and the water recoveredior reuse. Toaccomplish this purpose the'cornbus'tionv gases are saturated at thegenerator suiiiciently so that any sulphuric acid formed at any place inthe system will be so dilute asto be incapable of bringing about to anyappreciable extent corrosion lor other deterioration of the surfaceswith which the gases and condensate come into contact in thesystern. V c

It is the intention-to cover by patent all equivalents of the hereindisclosed method of operation and all modiiications thereof within thescope of the hereto appended claims.

We claim:

l. Method of utilizing combustion gases containing sulphur in suchmanner as to prevent core rosion or deterioration of surfaces with whichsaid gases come into contact which comprises: adding to the combustiongases such a relatively large quantity of water vapor thatk at allplaces Where condensation takes place water will be in excess ofsulphuric acid to dilute the acid to, a

substantially non-corrosive condition. v

2. Method of vutilizing combustion gasescontaining sulphur in suchmanneras to prevent coi'- rosion or deterioration of surfaces with whichsaid gases come into contact which comprises: adding to the combustiongases such Ia relatively large proportion of water vapor that theresulting water of condensation from the mixture of gases will containless than v1% of sulphuric acid.

3. Method of utilizing combustion gasesy yconc taining sulphurin suchmanner 4as to yprevent corrosion or deterioration of surfaces with whichsaid gases come into contact which comprises:

adding to the hot combustion gases water vapor,. which, at temperatureof -212 F. will constitute from 25%, by volume, to saturationV or" themixture.

lfl. Method of heating which comprises: circulating through a radiatingrsystem `combustion gases containing sulphur;y and mixingtherewith watervapor in such `quantity. that at all places where condensation takesplace', water will be suiciently in excessover sulphuric acid to dilutethe acid to a substantially non-corrosive condition. c

5. Method of heating which comprises: cir.- culating through a radiatingsystem combustion gases containing sulphur; andinixing therewith watervapor in such` quantity that the water :of condensation will containless than 1% of sulphuric acid. f r

6.' Method of heating which comprises: circulating through a radiatingsystemy combustion gases containing sulphur; and mixing` therewith watervapor which calculated at a temperature of 190-212 F. will consist ofbetween 25% and 50% of the volume themixture.

7 Method of heating which comprises: circulating through a radiatingsystem at an initial pressure "slightly below atmosphericpressure and atan initial temperature of between 190 andv 212 F., combustion gasescontaining sulphur and also containing water vapor in such quantity thatat all places where condensation 'takes place,

water will condense in suicient excess over sul-- phuric acid to dilutethe sulphuric acid to a s ubstantially non-corrosive condition. 8.Method of heating which comprises: circuusv .212 F., combustion gasescontaining sulphur and also containing Water vapor in such quantity thatthe mixture is substantially saturated as it enters the radiatingsystem.

9. Method of heating which comprises: circulating through a radiatingsystem at an initial pressure slightly below atmospheric pressure and atan initial temperature of about 190-212 F. a mixture of combustion gasescontaining sulphur and from 25% to 50%, by volume, of water vapor.

10. Method of heating which comprises: circulating through a radiatingsystem at a slight vacuum and an initial temperature of 190-212 F. whichis reduced to a ue temperature of F., a mixture of combustion gases,containing sulphur, and a water vapor in such quantity that thecondensate contains less than 1% of sulphuric acid.

11. Method of heating which comprises: circulating through a radiatingsystem a mixture of flue gases, containing sulphur, and Water vapor,which mixture is substantially saturated at the entering temperature ofsaid mixture.

12. Method of forming and utilizing for heating purposes a gaseousmedium comprising combustion gases 'containingsulphun which methodcomprises lowering the initial temperature of the medium by transferringto a body of water a portion of the heat from the combustion gasesdirectly after the combustion process to convert this water to waterVapor which is immediately added to the combustion gases in sufficientquantity so that at all places where condensation takes place Water willdilute the sulphuric acid to ay substantially non-corrosive condition.

13. Method of forming and circulating through a radiating system agaseous medium comprising combustion gases containing sulphur, whichmethod comprises lowering the initial temperature of the medium bytransferring to a body of Water 'a `portion of the heat from thecombustion gases directly after the combustion process to convert thiswater tov water vapor which is immediately added to the combustion gasesin suf- 'cientquantity so that at all places where condensationtakesplace water will dilute the sulphuric acid to a substantiallynon-corrosive condition, the medium beingformed and circulated undersub-atmospheric pressures by exhausting th-e non-condensible portion ofthe medium from the radiating system.

14. Method of forming and utilizing for heating purposes a gaseousmedium comprising combustion gases containing sulphur, which methodcomprises lowering the initial temperature of the medium by transferringto a body of water a portion of the heat from the combustion gasesdirectly after the combustion process to convert this water toWatervapor which is immediately added to the combustion gases to form amixed fluid heating medium having an initial temperature between 190 and212 F. and containing water vapor in sucient quantity so that at allpoints Where condensation takes place water will dilute the sulphuricacid to a substantiallynoncorrosive condition. i

15. Method `of forming and utilizing for heating purposes a gaseousmedium comprising combustion gases containing sulphur, which methodcomprises lowering the initial temperature of the medium by transferringto a body of water a lportion of the heat from the combustion gasesdirectly after the combustion process to convert this Water `to watervapor which is immediately added to the combustion gases to form a mixedfluid heating medium having an initial

